Waterproof paper and process of producing the same



UNITED STATES 1,706,840 PATENT OFFICE.

ALBERT L. CLAPP, or DANVERS', MASSACHUSETTS, assreuoa To BENNETT, mcoaro- RATED,

or BOSTON, MASSACHUSETTS,

A CORPORATION OF MASSACHUSETTS.

WATERPROOF PAPER AND PROCESS OF PRODUCING THE SAME.

Ho Drawing.

This invention relates to the preparation of a sized or waterproof paper in which is uniformly incorporated throughout a sizing agent, and more particularly an aluminum or other metallic soap, which has the property of rendering the paper non-absorbent and resistant to the passage of water,'ink, and other like aqueous liquids therethrough.

The sizing is usually carried out on the pulp stock in the beater engine, the sizing agent being incorporated into the stock in the form of a soluble soap during or after beating. The sizing is then effected by precipitatlng or fixing the size on the fibers by the addition of aluminum sulphate, alum or other soluble metallic salts .or mixture of salts. This causes the precipitation of an aluminum or other metallic soap in situ on all the fibers, producing a homogeneously sized stock. Paper formed from the sized stock, upon being dried, is non-absorbent and water-resistant.

T have found that straight chain fatty acid soaps, and more especially soaps pro duced from certain vegetable oils, e. g., linseed, cottonseed, palm, or China wood oils, and certain animal fats, e. g., stearin or olein, when employed for sizing pulp prior to its formation into paper, yield a sticky and tacky aluminum or other metallic soap which renders the stock tacky. Consequently, when such stock is subsequently formed into paper, it gums the wires of a Fourdrinier machine, or the wires of the cylinder mould and felts-of a cylinder machine, great difliculty being experienced in maintaining the paper-forming machinery in condition for effective operation. This 'difficulty accompanying the use of fatty acid soaps in large measure accounts for their heretofore relatively limited use in the sizing of paper.

I have discovered that I may advantageously employ soaps for sizing paper pulp which when used as ordinarily yield stocky and tacky aluminum orother metallic soaps, that render the paper-making stock sticky and tacky. This may be accomplished if the precipitation of the metallic soap on the stock is effected simultaneously with the precipitation of a non-adherent, flocculent precipitate, which envelops or films the sticky metallic soap particles so as to produce a non-sticky sized stock. Such a stock may be run on to the paper machine without difficulty.

ing in the beater.

' Application filed February 27, 1926. Serial No. 9 1,256.

The soap employed as a sizing agent may be produced as ordinarily by the saponification of olein, palmatin, or other suitable fatty acids or fatty acid esterswith caustic soda or other equivalent alkaline compound. The soap, is introduced into the pulp in the beater engine, together with a suitable quantity of a soluble reagent such as sodium silicate, which is capable of reacting with aluminum sulphate to yield a voluminous, fiocculent precipitate (of aluminum silicate when sodium silicate, and aluminum sulphate are used), which serves to envelop or film the aluminum soap particles, thus inhibiting a tackiness of the stock on which they become fixed. The precipitated aluminum silicate also serves as an excellent loading or filling material for the paper. It further serves better to pull down and fix the precipitated soap on the fibers, giving a high factor of soap-size retentivity by the stock.

In carrying out the process, ll may, for example, proceed about as follows: The beater engine is charged with sulphite pulp and the amount of-water necessary to insure its circulation is added. The pulp is then beaten tothe extent desired for paperforming operatiomduring or after the completion of which the sizing of the stock is effected.

The sizing soap is preferably added to the heater and incorporated into the pulp of an aqueous cream or paste. The aqueous sizing paste is uniformly admixed with the pulp prior to its precipitation in situ on the fibers. The addition of the sizing paste. after the beating operation tends to preventexcessive foaming. The paste may contain about 10 to 15 pounds of soap -(e. g., sodium stearate or sodium oleate, or a mixture of both) to 1,000 pounds of pulp, and about 15 to 20 pounds of sodium silicate (60 Baum). The paste may be prepared by dissolving the soap at about 220 to 250 F., in about 100 to 150 pounds of water, and adding sodium silicate to the soap solution thus formed. The paste is preferably allowed to cool prior to the addition to and incorporation. in the stock in the beater. The addition of a cooled aqueous paste diminishes the tendency to excessive foam- If desired, however, the

soap solution and sodium silicate may be separately added and incorporated into the stock in the beater.

After the soap solution and sodium silicate have been uniformly admixed with the pulp, the soap and sodium silicate are caused to react simultaneously by adding a solution of aluminum sulphate, or alum, to the beater engine, thus producing a voluminous mixed or composite precipitate of aluminum soa and aluminum silicate, which becomes fixed on the fibers, about to parts of alum insuring a complete precipitation. The precipitate consists of particles of aluminum soap, protected by a non-sticky film of aluminum silicate, which renders the fibers to which they become fixed non-sticky. While asmaller quantity of sodium silicate may be employed, it' is desirable to provide a sulficient amount of aluminum silicate to cover adequately the aluminum soap particles and -thus produce a substantially non-adhesive sized stock and much less regulated to produce the filling 7 Qtherfpulp can not safely be counted upon to produce the desired results.

The sized stock may be .formed into paper on a Fourdrinier or a cylinder machlne, without difliculty. The aluminum silicate, as precipitated, serves as an excellent loading or filling material, and imparts bulk and opaqueness to the pa er. a

The amount of SOdllllIl silicate introduced with the soap in the beater engine maybe desired, but, 1n any event,-enough sodium silicate should be added to insure successful pa er-forming machine operation. If desire the fatty acid soap may be replaced in part by rosin size.- In such'case the quantity of sodium silicate may be correspondingly reduced and.

thus the amount of filler or loading material 1n the fimshed paper present as" aluminum silicate may be regulated. Other loading or sizing agents also may be incorporated, together with those a ents mentioned.

While I have co ned myself to a s ecific example which has been found to yield the desired results for a certain paper product, it should be obvious that the condit1ons under which the process is carried out, and the proportion of the various agents employed may be changed, depending upon the characteristics desired in the finished paper. For nstance, in the preparation of wrapping papers I may employ kraft or sulphate pulp in the stock furnish and use other proportions of sodium silicate and sizing soap.

furnishes and a suitable proportlon o sizing soap and sodium silicate may also be employed.

In carrying out the sizing operation it is essential that the precipitation of the aluminum soa be effected simultaneously with the precipitation of the aluminum silicate, but it is not essential that the soap and sodium silicate be added to the stock in the beater en ine )rior to the aluminum sulphate. T us may first add the desired amount of alum to the stock and then add the mixed sodium silicate and soa paste thereto, but better results are obtalned by adding the alum subsequent to the incorporation of the sizing paste into the stock.

By the term soap as emplo ed in the specification and in the appen ed claims, unless the context indicates clearly to the contrary, I mean the saponified product of a straight chain fatty acid or fatty acid ester and which is capable of uniting with aluminum sulphate or other soluble metallic salts or mixture of salts to form a waterproof, insoluble, and sticky soap, as distinguished from sodium resinate, which has a ring structure and does not form a sticky soa under the same conditions. Among sucli soluble metallic salts ma be mentioned zinc sulphate," magnesium su phate and the like. These may be used together with a solutionof a suitable flocculating agent, to replace aluminum sulphate. Since there are various metallic soaps which may be produced, e. g., zinc stearate, magnesium resinate, aluminum palmitate and the like, having different characteristics, the characteristics imparted to the paper may be made to vary accordingly, depending upon the particular soap or mixture of soaps in the pa er.

claim:

1. A process of making paper, which comprises incorporating a soluble straight chain fatty acid soap into pa er pulp together with sodium silicate, adding metal salt in suflicient quantit to precipitate both the soap and the ium silicate, and running the pulp off on apaper machine.

2. A procem of making paper, which comprises lncorporating a straight chain fatty acid sodium soap into paper pulp together with sodium silicate, a ding alum in suflicient quantit to precipitate both the soap and the sodium silicate, and running the pulp off on a paper machine.

3. A process which comprises disseminating sodium stearate together with sodium silicate through cellulose pulp, adding alum in suflicient amount to react with both the sodium stearate and sodium silicate, and running the ulp out on a paper machine.

4. A sized and filled paper comprising aluminum stearate and aluminum silicate.

5. A sized and filled paper, comprising a straight chain fatty acid metallic soap and a metallic silicate.

6. A sized and filled pa r comprising a straight ,chain fatty aci aluminum soap and aluminum silicate.

In testimony whereof I have aifixed my signature. 

